Genetic Control Of Semen Production
North Carolina State University Swine Genetics Research from 2002. To evaluate the genetic control of semen production, specifically the number of services collected per ejaculate, semen collection records for 253 AI boars were obtained from Tyson Foods. Statistical analyses were conducted using the DxMrr random regression routines developed by Meyer (1998). The mean number of services per ejaculate produced during each month of age was determined for ejaculates that were previously standardized for sperm concentration. Mean observations were then limited to those from 6 to 27 months of age on 3- month intervals. Genetic parameters were estimated for average number of services per ejaculate by age of boar classification using a model that included season and year as fixed effects, additive genetic effect of the boar, permanent environmental effect of the boar and random error. Number of services per ejaculate was highly heritable with a mean heritability of .44 across all age classifications. Heritability for number of services per ejaculate was quite uniform across age of boar classification indicating that the genetic control of number of service per ejaculate is similar for boars of any age. Genetic correlations between different age classifications for number of services per ejaculate were close to one for adjacent observations but decreased as the period between observations increased, especially after 12 months. While further investigation is warranted it would appear that the opportunity does exist to evaluate and select AI boars for semen production.